var maxInterval = 60 * 120 * 1000; // 120 min
var startTimeSec = new Date().getTime();
var timerInterval = 60 * 0.5 * 1000; // 30 sec
var refresheTimerInterval = 60 * 10 * 1000; // 10 min
var lastRefresheTimer = startTimeSec;
var sessionTimer = setTimeout('sessionPing()', timerInterval);

function sessionPing() {
	if(new Date().getTime() - lastRefresheTimer>refresheTimerInterval){
		lastRefresheTimer = new Date().getTime();
	    var myAjax = new Ajax('/session_util/session_ping.jsp', {method: 'get'});
	    myAjax.request();
    }else{
    }
    if((new Date().getTime()) - startTimeSec<maxInterval){
        sessionTimer = setTimeout('sessionPing()', timerInterval);
    }
}